A high-density material is used for various purposes. As one typical application, it is widely used as a nuclear-radiation-shielding material. In radiation treatments or radiation-based measurements, a portion of a subject having no need for radiation exposure is covered by a shield member for shielding radioactive rays. Lead has heretofore been used as the material of such a shield member, in view of its advantages, such as high radiation-shielding effect, low cost and excellent workability. However, lead itself has harmful effects on the human body, and involves issues related to environmental pollution.
In order to provide an alternative material for solving the problem of lead, there has been proposed a high-density metal excellent in deformability and workability, particularly, a complex of tungsten and rubber-like organic material. For example, Japanese Patent Laid-Open Publication No. 10-153687 discloses a flexible material having a high density of 9 g/cm3 or more, which is prepared by mixing rubber with other organic materials. While this invention is intended to achieve increased density by use of two kinds of high-density powders different in mean particle size, the obtained material is lower in density and inferior in radiation-shielding function as compared to the conventional lead.
In addition to the use for a nuclear-radiation-shielding material, a high-density material is also used as a vibration-insulating material or a weight for maintaining the balance of an object. In terms of the use for such a vibration-insulating material or a balancing weight, the high-density material disclosed in the above material is insufficient in density, flexibility and workability.